JPS5821527A - Fourier converting type infrared spectrophotometer - Google Patents

Abstract

PURPOSE:To facilitate adjustment through a simple structure, by detecting a position of a moving mirror of an interference meter and center position of the moving mirror by the use of a laser light flux and a white light flux. CONSTITUTION:Light from a white light source S3 produces a parallel light flux omega by a lens, the light flux omega and a light flux emitted from a laser source S2 are parallel to each other, and are adjusted so that they are brought to a parallel to a measuring infrared light flux entering a translucent mirror BS from a collomater CM. 3 types of light fluxes enter the translucent mirror BS, a part of them reflect, a part of them transmit, they independently interfer, and are radiated from an interference meter. Laser rays emitted from the interference meter are reflected in a direction of a samle chamber SC without a change in the direction thereof. In order to detect a center position of a moving mirror Mm, a position, where an output of a photo detector D2 is maximized, is detected by lighting a white light source S3 and by moving mirror Mm. The position of the moving mirror Mm is detected by detecting laser rays by a photo detector D3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Fourier transform infrared spectrophotometer. Fourier transform infrared spectrophotometers use optical methods to detect the center position of the moving mirror and obtain signals indicating the position of the moving mirror, but this method is structurally complex and difficult to adjust. .

The present invention aims to eliminate the above-mentioned structural complexity in a Fourier transform infrared spectrophotometer and to facilitate adjustment. In order to concretely explain the purpose of the present invention, a conventional example will be described. FIG. 1 shows the configuration of a conventional Fourier transform spectrophotometer. L is a light source, CM is a collimator mirror that converts the light emitted from the light source into a parallel beam, and inputs it into a semi-transparent mirror BS placed at an angle of 45 degrees.8Mf is a fixed mirror, and Mm is a movable mirror. The semi-transparent mirror BS constitutes a Michaelian interferometer. SC is a sample chamber in which the light flux emitted from the above-mentioned Michelson interferometer is divided into a reference light flux R and a sample light flux S, a control cell and a sample cell are placed in the optical path of each light flux, and the transmitted light is transmitted to a photodetector p1. to receive and measure light. When the optical path lengths from the center point of the semi-transparent mirror BS to the mirrors Mf and Mm are equal (1.1'), all wavelengths of light from the Michelson interferometer are intensified, and the intensity of the output light is maximum. Become. Moving mirror M at this time
Let the position of m be the center point. When the movable mirror is moved from the center point, the light emitted from the interferometer weakens, and the distance the movable mirror moves until it is strengthened again by interference is half the wavelength of the light.
Therefore, the intensity of the emitted light varies depending on the wavelength, and the change in the intensity of the emitted light when the movable mirror is moved is a waveform in which countless cosine waves with continuously different frequencies are superimposed with their origins coincident.The spectrum of a multi-light source. The waveform is obtained by Fourier transform. When the emitted light from such an interferometer is guided into the sample chamber and transmitted through the sample, a Fourier transformed waveform obtained by superimposing the spectrum of the light source and the absorption spectrum of the sample is obtained as the output of the photodetector D1. By converting, the absorption spectrum of the sample can be determined.

Conventionally, in order to detect the center position of the movable mirror Mm with the above-mentioned configuration, the back surface of the movable mirror Mm is connected to a mirror Mm' parallel to the front surface.
A second Michelson interferometer is constructed together with the semi-transparent mirror BSI and the fixed mirror Mfl, and at the center position of the movable mirror Mm where l and j" in the figure are equal, the movable mirror M shown in FIG.
m', the optical path length r of the semi-transparent mirror BSI, the fixed mirror Mfl and B
The optical path length rl& with SI is made equal, in other words, the movable mirror Mm' is also positioned at the center point, white light is made incident on this second Michelson interferometer, and the emitted light is sent to the photodetector D2. The second Michelson interferometer must be adjusted so that when the position of the moving mirror Mm that shows the maximum peak is detected, the moving mirror Mm' is also at the center point. However, this adjustment is difficult and has resulted in an increase in the price of the equipment.

In addition, in order to know the amount of movement of the movable mirror Mm, a signal is output every time the movable mirror moves a certain distance.
f2 constitutes a third Michelson interferometer, a laser beam is input, the light emitted from this interferometer is measured by a photodetector D3, and a signal is output every time the movable mirror Mm moves a certain distance. ing. Such a third Michelson interferometer also complicates the device structure.

Furthermore, in the case of infrared spectroscopy, the semi-transparent mirror BS is made of an infrared-transmissive material such as KBr deposited with Ge to make it semi-transparent to infrared rays, but this semi-transparent mirror transmits almost no visible light. Since it does not pass through the translucent mirror BS, it is difficult to adjust the optical system located behind the semitransparent mirror BS.

The present invention aims to solve the above-mentioned three problems, and eliminates the third interferometer mentioned above, and uses white light to detect the center position of the movable mirror in addition to the measurement light in the main interferometer. The present invention also provides a Fourier transform infrared spectrophotometer that can also input a laser beam for obtaining a signal of the position of a moving mirror. The present invention will be explained below with reference to Examples.

FIG. 2 shows an embodiment of the invention. BS is a semi-transparent mirror, M
f is a fixed mirror, Mm is a movable mirror, and these three components constitute an interferometer. Md is a mirror that guides the emitted light from the interferometer to the sample chamber SG. Sl is an infrared light source for measurement, and is reflected off the collimator mirror CMK to form a parallel beam of light, which is made incident on the semi-transparent mirror BS. S2 is a laser light source, 83 is a white light source, and E12.83 are arranged above and below the plane of the drawing, and the light from the white light source S3 becomes a parallel light beam W through the lens. This luminous flux W and the luminous flux emitted from the laser light source si are parallel to each other, and the collimator mirror CM
It is adjusted so that it is parallel to the measuring infrared light flux that enters the semi-transparent mirror BB.

As shown in FIG. 3, the luminous flux emitted from the laser beam [82, passes through the through hole h1 provided at the center of the collimator mirror CM and is made to enter the center of the semi-transparent mirror B8. As shown in Fig. 3, the white light flux W passes through the collimator mirror C.
The light is incident near the upper edge of the semitransparent mirror BS, which is made higher than M in the plane of the drawing. This part of the semi-transparent mirror BS is made to be semi-transparent to white light. With the above-described configuration, three kinds of light beams are incident on the semi-transparent mirror BS in parallel with each other, are partially reflected and partially transmitted, interfere independently with each other, and exit from the interferometer. Among these emitted lights, white light is transmitted through semi-transparent mirror BS, fixed mirror Mf, and movable mirror M as well as collimator mirror CM.
The light passes over the mirror Md, which is made lower than m, and enters the white light photodetector D2. Similarly, the beam of laser light emitted from the interferometer passes through the through hole h2 at the center of the mirror Md and is made to enter the photodetector D3. The infrared light for measurement is mirror M(l
The light is reflected by the sample chamber SC and is incident on the photodetector D1. The mirror Md can be slid in the mirror direction within the same plane as the mirror surface without moving the mirror surface back and forth, and the through hole h2 can be removed from the laser beam. When the through hole h2 is removed from the laser beam, the direction of the laser beam emitted from the interferometer changes.In order to detect the center position of the movable mirror Mm with the above-described configuration, the white light source S\ is turned on and the movable mirror is moved. It is sufficient to detect the position where the output of the detector D2 is maximum. When adjusting the position of the optical elements of the optical system from the semi-transparent mirror BS to the measurement photodetector, the laser beam is transmitted through the mirror M path to the photodetector D1. is visible, making it much easier to adjust the position of the optical element. To obtain a signal of the position of the movable mirror Mm during measurement, slide the mirror Md so that the through hole h2 at the center of the mirror Md is within the optical path of the laser beam, and the laser beam emitted from the interferometer is incident on the photodetector D3. Then, a scale signal corresponding to the amount of movement of the movable mirror is obtained by periodic changes in the output of D3 due to the interference of laser light in the interferometer.

The Fourier transform infrared spectrophotometer of the present invention has the above-mentioned configuration and does not have the second and third interferometers, so it is very simple in terms of structure and adjustment. Visible light can be used to adjust the optical system before leaving the room, making this adjustment easier.

[Brief explanation of the drawing]

Figure 1A is a plan view of the conventional example, Figure 1B is an enlarged view of the main parts,
FIG. 2 is a plan view of an apparatus according to an embodiment of the present invention, and FIG. 3 is a perspective view of a collimator mirror in the above embodiment. BS...Semi-transparent mirror, Mf...Fixed mirror, Mm...Moving mirror, SC...Sample chamber, Sl...Infrared light source for measurement, S2...White light source, S3... Laser light source, D
I, D2゜D3...photodetector.

Claims (1)

[Claims] The laser beam and the white light beam are made to enter the same interferometer in parallel with the measurement infrared beam, and the laser beam is located at the center of the measurement beam, and the white light beam is located at the outer edge of the measurement beam. A mirror is slidably inserted parallel to the mirror surface into the optical path of the light emitted from the interferometer to reflect the light emitted from the interferometer toward the sample chamber. A light part is provided so that during measurement, the laser beam passes through the transparent part and enters a photodetector for the laser beam installed behind the mirror, and the same mirror is used to adjust the optical system after the interferometer. At the other position where the mirror is slid, the laser beam is reflected by the same mirror and enters the sample chamber in parallel with the measurement beam, and the white light beam is positioned relative to the position of the mirror. The laser beam passes straight through the outer edge and enters the white light beam photodetector, and the laser beam photodetector obtains a signal indicating the position of the movable mirror of the interferometer.The white light beam photodetector outputs the above signal. A Fourier transform infrared spectrophotometer characterized by obtaining a signal for detecting the center position of a movable mirror.